The present invention relates to the filling of valve bags with particulate material and, more particularly, to a method and system for controlling a novel filling nozzle which eliminates the sifting of product from the valve bag during and after the bag filling operation.
Particulate materials are commonly packaged in bags that are made from multiple layers of paper and have a "valve" in one upper corner. The valve provides an opening through which the material is dispensed during the bag filling operation. The valve bag is typically filled by inserting a spout or nozzle into the valve and causing material to flow through the nozzle into the bag. When the bag is full, the flow of material is halted and the nozzle is withdrawn from the valve usually by moving the bag away from the nozzle. The valve is sealed to prevent egress of the material from the bag during shipping and handling.
The control system and method of the present invention is particularly suited for use in conjunction with the filler sleeve disclosed in co-pending U.S. patent application Ser. No. 300,038 filed Sept. 8, 1981. The filler sleeve comprises an elongated tubular member which is connected to the top end of the bag. The tubular member includes an open end which is contiguous with a filler opening provided in the top end of the bag. The opposed end of the tubular member is closed, e.g. by heat sealing or folding. A longitudinally extending slit is provided in the tubular member disposed on the bottom surface thereof. In use, when the bag is filled by introducing the product by air flow or by gravity through a filler nozzle which is inserted into the filler opening and into the tubular member, the product is deflected downwardly into the bag thereby inhibiting the likelihood of blow-out of the side panels. Preferably, the tubular member is formed from a stretchable material such as polyethylene, so that during the filling of the bag the flow of the product stretches the material. By this arrangement, when the filling is completed, and the bag is inverted, the side edges of the slit, which have been stretched, overlap and the weight of the product functions to maintain the overlapping relationship thereby preventing the unwanted escape of product from the bag.
While the filling nozzle of the present invention is particularly suited for use with the slitted filler sleeve disclosed in the aforementioned copending application, those skilled in the art will appreciate that the present filling nozzle is also adaptable for use in conventional valve bags.
In filling valve bags, problems have been encountered in reducing or eliminating the sifting and dusting problems which occur. Typically, some amount of product will spill from the filling nozzle on its way into the bag or on its withdraw from the bag. Various hazardous products, such as toxic chemicals, clay, limestone, cement, carbon black, herbicides, fungicides, and the like are usually packaged in valve bags and the elimination of product sifting and dusting problems during the filling operation is therefore imperative. The slitted sleeve enhances bag performance and effectively reduces dusting, but does not completely eliminate the problem. Further, sifting can occur after the filling process is completed, e.g. during transit, if material is entrapped in the valve during the filling process. Such entrapment of material can occur if the filling nozzle does not directly discharge product through the slitted sleeve. Material can also become entrapped if product dribbles out of the nozzle into the sleeve at the end of the filling cycle.
It would be advantageous to provide an apparatus and method for filling a valve bag which directs the flow of product downwardly into the bag, thereby avoiding the direct discharge of product into the back end of the valve bag sleeve. It would be further advantageous if the apparatus and method included a purge system to clear the filling nozzle of all product after a bag has been filled, to substantially reduce product dribble out of the nozzle, and to clear any product from the valve sleeve which remains after the bag has been filled.
This invention relates to such an apparatus and method.